1. Field of the Invention
This invention relates to surgical instrumentation and more particularly to a trocar-type instrument and method for incising a pathway through tissue overlying an anatomic cavity and for placing a trocar sleeve or cannula within the incised pathway to provide access to the interior of the body.
2. Description of Prior Art
In abdominal "endoscopic" surgeries, a surgeon typically insufflates the abdominal cavity with CO.sub.2 gas to separate the abdominal wall from viscera. A trocar then is used to puncture a pathway through tissue overlying the abdominal cavity and to place a trocar sleeve in the abdominal wall. A trocar is a shafted instrument typically configured with a three-faced pyramidal piercing tip from which the name trocar is derived: trois (three) and carre' (sides or faces). Trocars suffer from the disadvantage of requiring powerful thrusting forces to puncture a path through tissue. The sharp tip and edges of the trocar can cause injury to an internal organ upon the slightest contact.
Commercially available safety trocars typically use a spring-loaded protective shield that springs forward to cover the sharp tip after the tip enters the abdominal cavity. Attempts to shield trocar tips within axially-reciprocating shields after penetration into an anatomic cavity are undesirable because the trocar tip must pierce fully into the cavity before the shield is triggered. Such trocars also rely on insufflation to prevent a trocar tip from lacerating internal organs. Insufflation is undesirable because it is time-consuming. There is therefore a need for new instruments and methods for safely incising a path through body wall with or without insufflation.